SLAC recently launched the ultrafast electron diffraction and microscopy (UED/UEM) Initiative, with the goal to develop the world’s leading ultrafast electron scattering instruments, which are complementary with x-ray free-electron lasers such as LCLS and LCLS-II. The first step of the Initiative is a MeV UED system which is now actively supporting an ultrafast science program, and at the same time serving as a testbed for instrumentation development.
In this talk, design of the SLAC MeV UED system will be briefly introduced. Key machine performance parameters will be reviewed, including machine stability and reproducibility, as well as reciprocal-space and temporal resolution. Ultrafast dynamics from a variety of samples, including 2D materials, thin nanofilms, nanoparticles, and gas-phase molecules have been studied using this machine. Selected ultrafast science experiment results will be presented. In the meantime, much R&D efforts have been devoted for novel machine capabilities to enable new science opportunities. For example, we have experimentally demonstrated a femtosecond MeV electron microdiffraction, which is capable to resolve local structure from single crystal of μm lateral size with 100 fs root-mean-square temporal resolution. Future developments include 10-fs temporal resolution UED, THz pumping capability, etc. We will also discuss R&D towards the next step of the Initiative, which is to develop key technologies for future UEM with unprecedented combined spatial-temporal resolution. This R&D will focus on a superconducting radio-frequency photocathode gun, which features high accelerating field hence high beam brightness, excellent energy stability, and outstanding flexibility in bunch length from picosecond to a hundred picoseconds.